Methamphetamine-Induced Rapid and Reversible Changes in Dopamine Transporter Function: AnIn VitroModel

Abstract

This laboratory has demonstrated that a single methamphetamine (METH) injection rapidly and reversibly decreases the activity of the dopamine transporter (DAT), as assessedex vivoin synaptosomes prepared from treated rats. This decrease does not occur because of residual drug introduced by the original injection or nor is it associated with a change in binding of the DAT ligand WIN35428. The purpose of this study was to elucidate the mechanism or mechanisms of this METH effect by determining whether direct application of this stimulant to synaptosomes causes changes in DAT similar to those observedex vivo. Similar to theex vivoeffect, incubation of striatal synaptosomes with METH decreased DAT activity, but not WIN35428 binding: the effect on activity was not eliminated by repeated washing of synaptosomes. Also, as observedex vivo, incubation with 3,4-methylenedioxymethamphetamine, but not cocaine or methylphenidate, caused a METH-like reduction in DAT function. The rapid and reversible METH-induced diminution in DAT activity did not occur because of a change in membrane potential, as assessedin vitroandex vivoby [³H]tetraphenylphosphonium accumulation. However, the METH-related decline in DAT function may be attributed to phosphorylation because NPC15437, a protein kinase C inhibitor, attenuated the METH-induced decline in DAT function. Similarities between previously reported effectsex vivoof a single METH injection on serotonin and norepinephrine transporter function and effects of direct METH applicationin vitrowere also found. Together, these data demonstrate that thein vitroincubation model mimics the rapid and reversible effects observed after a single METH injection.